PROJECT SUMMARY This project aims to fill the urgent need for a safe and engaging intervention that promotes physical activity in a population of patients with chronic diseases (e.g., diabetes, asthma, osteoarthritis, and chronic heart failure). Compelling evidence suggests that physical activity is an effective therapeutic intervention for numerous chronic diseases. However, in spite of the wide consensus that physical activity should be an integral treatment component for many chronic diseases, most patients remain inactive1 due to a variety of barriers and obstacles they regularly encounter. We therefore propose to innovatively adapt an efficacious exercise-promoting intervention that targets sedentary employees2 to a population with specific needs and constraints that result from chronic disease and deliver this intervention as a mobile application that can be accessed via smartphone, tablet, or computer. We propose a program design that follows recommendations derived from a recent NIH-funded meta- analytic review of interventions to promote physical activity in patients with chronic diseases, which emphasizes the importance of behavioral activation as opposed to cognitive-behavioral intervention features.3 Our comprehensive mobile application is therefore composed of (a) an initial screening; (b) baseline physical activity (PA) levels recorded via wireless accelerometer device; (c) an assessment that elicits information regarding preferences for and barriers to PA; (d) goal setting; (e) daily e-mail or text messages stating the goal for the day, the type of exercise, and a link to a video demonstrating the exercise; (f) a brief check-in to determine whether the user is currently encountering a barrier (pain, fatigue, etc.) and tailored remediation for the barrier through social media functionality and expert advice; (g) prompts to execute the daily exercise; (h) integration of a wireless accelerometer device (e.g., Fitbit(R)) to supplement self-reported exercise data and to drive tailored feedback and goal setting; (i) check-in regarding activity completion (e.g., have you completed the exercise?, did you enjoy this exercise?, do you feel better after this exercise?); (j) immediate, personalized feedback on how executed physical activities contribute to goal progress; and (k) feedback reports for the primary care physician. Together these design features will promote and support a sustainable habit of regular PA in this vulnerable population. In a 30-day pre-post study, we will test preliminary efficacy and feasibility of this prototype intervention in a population of 38 adult patients with chronic osteoarthritis. The Phase I prototype program will be limited to demonstrating feasibility with individuals with osteoarthritis to control the overall scope of the Phase I project. We hypothesize that this intervention will engage this population and increase subjects' PA level from pre- to post-assessment. If this pilot efficacy trial yields satisfactory results, the Phase 2 project will expand the scope of the program to include all patients with additional chronic diseases (e.g., osteoarthritis, hypertension, diabetes, pulmonary disease).